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June 30, 2008 <br />IV. Pros and Cons <br />Pros <br />• Provides an additional tool for protecting flows outside of the CWCB instream flow <br />program; depends on voluntary, market -based transactions among water users rather <br />than a regulatory approach. <br />• Offers flexibility in structuring transactions to match demands. <br />• Provides multiple benefits by enhancing flows in the protected segments while also <br />allowing the water to be consumptively used below those segments. <br />Cons <br />• Some water rights are not decreed for downstream use. <br />• There may be potential difficulty in ensuring administrative control of the water <br />against intervening diversions that might be able to provide a substitute supply below <br />the protected segment. <br />The timing of the deliveries would need to be structured to match the demand pattern <br />of the ORVs. <br />2. EXISTING WATER RIGHTS <br />I. Basic Concept <br />The two main calling water rights on the main stem of the Colorado River are the <br />Shoshone Rights and a group of rights known as the Grand Valley rights or the Cameo <br />Call, actually 3 different structures. The Shoshone rights are capable of calling for water <br />year round (1250 to 1408 cfs), while the Grand Valley rights are irrigation rights which <br />can only call for water April through October. These are absolute water rights, which <br />under dry to average hydrologic conditions may govern the flows on the Colorado River <br />through Glenwood Canyon during portions of the year. The Shoshone senior right is the <br />focal point of this concept as it is the most senior water right and located at the bottom of <br />the study area. However the Grand Valley rights do receive the delivery of the supplies <br />from the Green Mountain Reservoir Historic Users Pool (HUP). <br />II. Benefit to Stream Segments <br />The year round utilization of the Shoshone right has the ability to keep flows of around <br />1250 cubic feet per second (cfs) in the Colorado River at the Dotsero gage. The <br />Shoshone right is more protective for the Glenwood Canyon segment. The Grand Valley <br />rights call for water from all upstream junior rights. During portions of the year, flows on <br />the Colorado River have historically been maintained by the operation of the Shoshone <br />rights, and to a lesser extent the Grand Valley rights. <br />III. Permanent Flow Protection <br />When operating at full capacity, the Shoshone rights offer year round protection in the <br />operation of existing water rights administration. The administration of these rights has <br />IM <br />